Patent GB-456981-A (GB)
Title: Improvements in or relating to impulse repeating arrangements for use in telephone or like systems
IPC: H04Q1/36
Filed: 1935-05-18
Abstract: 456,981. Automatic exchange systems. ASSOCIATED ELECTRIC LABORATORIES, Inc., 1033, West Van Buren Street, Chicago, U.S.A. May 18, 1935, No. 14597. Convention date, May 19, 1934. [Class 40 (iv)] The line relay 207 of a connecting link controls a pulse relay 303 which in turn controls a repeating relay 309 the arrangement being such that the repeating relay operates at each odd impulse of a digit and de-energizes at each even impulse to ground alternately corresponding old and even pulse conductors, and the pulse relay is controlled by the repeating relay in such a way that it cannot reoperate after responding to an impulse until the repeating relay has also operated. The line relay, on release at an impulse, may close a high-resistance priming circuit to assist its re-energization on a leaky line. The invention is described with reference to a small all-relay automatic exchange which also comprises the following features : (1) The connecting links comprise sets of group and unit relays at each end, operated in succession first to find a calling or wanted group and then a calling or wanted line in that group, the relays in each set being arranged in the form of a chain. Each element of the chain comprises two relays, one operated in its turn in the chain to connect up the test conductor only, the other being operated only after a calling or wanted line has been found to switch through the speaking conductors ; (2) Party-line code ringing is determined by an extra digit and may also be determined by the units digit in the case of 20-party lines. The extra digit or the tens or units digit may also determine to which side of the line the ringing current is to be applied; (3) The busy test of a party-line is initiated as soon as the first impulse of the extra digit is received the busy relay (twostep) being connected in series with the test relay (marginal) at this time. At the end of the digit, either the busy relay operates fully to connect up busy tone or the test relay operates due to the removal of the busy relay from its circuit; (4) A number of link circuits are arranged in a chain the starting arrangement being such that successive calls are connected alternately to the beginning and the middle of the chain. If a calling line is not found, a new link circuit is automatically allotted ; (5) For calls to a distant exchange, the feed in the local link is cut out. Non-numerical switching. Line relay 1 of subscriber S, Fig. 1, grounds start lead 61 to operate relay 510 in the allotter AR and ground is thereby extended over lead 281 to operate line relay 207 in the next available link-circuit. Relays 303, 301, 302 operate and ground from armature 228 is extended over leads 275, 153, 156 to operate relay 111 of the pair 110, 111 appertaining to the first tens group. Relay 111 extends lead 156 to relay 121 of the second tens group and so on, each relay being slow to pull up to allow time for the group test relay 203 to operate. When the calling tens group is found, in this case the first, relay 203 operates over lead 159 and the grounded start lead 61 transferring grounded lead 153 from the group relays FGR to the units-relay group FUR. Relay 111 remains operated connecting the test conductors of lines of the first tens group to armatures of the units relays 101 .. 107. Relays 101 .. 107 operate in succession similarly to relays 111 ... 181 and when the calling line is found, units test relay 204 operates over lead 152 and armatures 174, 114 in series with the cut-off relay 2. Relay 110 operates to switch through the talking conductors and line relay 207 is now operated over the calling loop. Relays 3, 312, 202, 201 also operate, the last-mentioned transferring the lead 281 to the next link-circuit in the chain. Relays 520,530, however, controlled by relay 510, interact to direct the next call over lead 281<1> to a link in the middle of the chain. When all links are busy, relay 500 operates over a chain circuit to de-energize the transfer relays 201. Tens and units selection. At the break of the first impulse of the tens digit, relays 207, 303 release, the former completing a priming circuit for itself over resistance 319 and back contact 231 to assist re-energization of the relay on leaky lines. The release of 303 energizes relays 306, 307, 309 of which 307 remains up during impulsing owing to its slow-release characteristic and locks up 306. Relays 307 and 309 complete a circuit over leads 391, 389, 278 for the first tens-group connecting relay 411. At the end of the first impulse, relay 303 re-operates over contacts 347 (back) and 350 (front), completing a locking circuit for the lower winding of 309 and an energizing circuit for relay 308 over contacts 351, 338, 326. Relay 304 also operates to cut off dial-tone DT. At the break of the second impulse, the release of 303 causes 309 to release and 308 to lock, the release of 309 transmitting a pulse from ground 376 over the even pulse lead 386 to the second tens relay 421. At the end of the second impulse, relay 303 re-operates over contacts 347 (front) and 350 (back) and releases relay 308. Relays 308, 309 act similarly for succeeding impulses, the operation of 309 at each odd impulse grounding the odd pulse lead 384 and its release at each even impulse grounding the even pulse lead 386. The dependence of the re-energization of 303 upon the contacts 347, 350 of 308, 309 ensures correct operation over lines of varying characteristics. If the tens digit is assumed to be 7 (for a call to subscriber S4 on line 71) relay 471 remains locked and at the end of the digit relays 307, 306 release and an alternative locking circuit for relay 312 is closed over the lower winding of relay 311 which switches over from the tens control conductors to the units control conductors. Units selection takes place in a similar manner to tens selection, relay 401 remaining locked when the units digit is 1. At the response of 306 at the beginning of the digit relay 312 is released and at the end of the digit 311 is also released to switch over to the code-ringing control relays CSR, Fig. 6. Party-line ringing. An extra digit is repeated by relays 207. 303, 309 in similar manner over odd and even pulse leads 398, 397 to relays 610 .. 660 of which relay 660 is locked for digits of six or over and relays 610 .. 640 are used a second time for digits 7 .. 0. For calls to certain 10-party lines such as No. 71, five bells are connected to each leg and for final digits of six or over relay 314 which reverses the ringing connections is energized over contact 666 of relay 660 and contacts 438, 457 of the tens and units relays corresponding to the line. Other lines having twenty parties are selected by two different numbers e.g. 26 and 27, the connecting relays 421, 407 for one of these numbers causing the operation of relay 600 which connects up a further series of ten codes. If the called line is idle, marginal test relay 315 operates when relay 306 releases at the end of the digit, operates connecting relay 470 which extends the speaking conductors, and completes a circuit for the pick-up relay 670 from lead PU. Ringing relay 313 is then operated in accordance with the selected code and a slow relay 310 lagging behind the ringing relay connects ring-back-tone to the calling party and battery over resistance 355 to conductor 253 to discharge the ringing condensers. When the called subscriber replies relay 211 operates connecting up 210 which removes a short-circuit from relay 208 to permit its operation if the calling line is a loop. Relay 212 is operated when the called line is a loop. Relay 209 operates, to give reversal-supervision, over lead 158 and contacts of a group relay if the calling line is in a group requiring such supervision. Called line busy. The condition of the called line is tested during the receipt of the final digit by the connection of the marginal test relay 315 to the test wire 382 over one of armatures 611 .. 661, resistance 341, and busy relay 305. If the line is busy, relay 305 operates partially and, on the relapse of 306 at the end of the digit, operates fully over its locking circuit and connects up busy tone BT. Reverting call. The wanted number is dialled as before and the calling party hangs up on hearing busy tone. Relays 207, 303 release but 302 is held energized over a circuit 272, 152, 9, 16 (Figs. and 4), 382, 332, 324. Reverting call relay 205 then operates over the circuit 273, 271, 152, 16, 324, releases relay 110 to disconnect the line from the link conductors 150, 151, and completes a circuit for the test relay 315 which initiates ringing as before. When either subscriber replies, relays 211, 212 operate followed by 210 which releases 302 and the link. Conversation takes place over the line circuit only, feed current being supplied by the line relay 1 which on operation marks the line busy to incoming calls and holds operated a further relay 3 which disconnects the start-wire 61. Call to distant exchange. An outgoing trunk is reached by dialling 81 and for such a call switch-through relay 213 operates over the circuit 249, 221, 259, 340, 269, 270, 445, 382 in series with the cut-off relay associated with the junction. Relay 213 cuts out repeating coil RC and completes a circuit for relay 480 so that the calling line is connected through to the distant exchange. Relays 213, 302, 2 are held by ground sent back over lead 487. For calls to ring-down trunks, relay 302 is held by relay 212 under control of the distant operator. Irregular operation. (1) Interrupter contacts 593 operate relay 590 once every two seconds. At any such operation slow-release relay 580 transmits a battery pulse over lead 285 to operate relay 206 if relays 211, 212 and 213 are all unoperated. Relay 206 transfers the holding ground to armature 592 so that if the relays are still unoperated when contacts 593 next close, the link circuit is released. This r